Portable Emission Measurement System Research Articles

A Study on Emission Measurement Method by Using Automated Intermittent Sampling for Real Driving Emissions of Gasoline Passenger Vehicles, Including Hybrid Electric Vehicles and Plug-in Hybrid Electric Vehicles

<div class="section abstract"><div class="htmlview paragraph">Electric vehicles have become more widespread globally, with the aim of realizing a carbon-neutral society. In addition, the various policies for vehicle engines have become increasingly strict. It is desirable to evaluate fuel consumption and exhaust emissions using real vehicles on actual roads, with the goal of improving air quality. Hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs) have a high frequency of engine stops during driving. In a real driving emission (RDE) test, a portable emission measurement system (PEMS) is used, which continues to measure emissions even when the engine stops; this can decrease the emission concentration inside the tailpipe and result in an inaccurate emission measurement. Furthermore, RDE tests are affected by the installation performance of the PEMS; the emission intake is often installed by extending the exhaust outlet. Gasoline vehicles have specific emission characteristics that pose an issue when the tailpipe at the muffler outlet is extended and the measurement is made after merging.</div><div class="htmlview paragraph">This study thus examines the methods for constructing the high-precision PEMS necessary for RDE evaluations for the increasingly common HEVs and PHEVs. In particular, the emission rates and sampling locations are investigated, and a method for operating the emission analyzer intermittently to synchronize with the engine is examined and evaluated.</div></div>

Exhaust Emissions of In-Use Euro 6d-TEMP and Euro 6d Vehicles in WLTP and RDE Conditions, a Comparison

<div class="section abstract"><div class="htmlview paragraph">Air pollution is a major threat to the environment and human health being responsible of more than 350 000 premature deaths every year in the European Union (EU). Road transport accounts for circa 40% of the total NOx emissions and 10% of the particulates emissions of the EU. However, these shares increase significantly in urban areas where 75% of the citizens live. In order to curb pollutant emissions from new vehicles entering the European market, the Euro 6 regulation, setting emission limits for cars and vans, was recently updated with the introduction of a new test procedure in the laboratory, the Worldwide Harmonized Light Vehicle Test Procedure (WLTP), and a novel on-road test performed with Portable Emissions Measurement Systems, the Real Driving Emissions regulation (RDE). Both test procedures WLTP and RDE were designed to represent typical driving conditions and thus help characterizing exhaust emissions of light-duty vehicles in real life operation. This manuscript presents NOx, CO, and solid particulate number PN emissions of 53 gasoline and diesel passenger cars type-approved in the EU after the entry into force of the WLTP and RDE (i.e., meeting the Euro 6d-TEMP and Euro 6d standards). Emissions data over WLTP and RDE tests on in-use vehicles was collected by the Joint Research Center (JRC) of the European Commission in the period 2018-2021. Emissions are characterized by powertrain, fuel type, and test procedure. All vehicles comply well with Euro 6 emission limits and no statistically significant differences are found in NOx, CO, and PN emissions measured over the complete WLTP and RDE tests, both for gasoline and diesel vehicles.</div></div>

The impacts from cold start and road grade on real-world emissions and fuel consumption of gasoline, diesel and hybrid-electric light-duty passenger vehicles

Progressively stringent regulations regarding vehicle emissions and fuel economy have spurred technology diversification in light-duty passenger vehicles (LDPVs). To assess the real-world emissions and fuel economy performances of hybrid electric vehicles (HEVs) compared to conventional internal combustion engine (ICE) vehicles, on-road measurements of ten gasoline, four diesel and six full hybrid LDPVs were performed using portable emissions measurement systems (PEMS) in Macao, China. The hot-running emission results indicate that the high emission risks of gasoline vehicles are associated with high mileage and old model years. Diesel vehicles are found to be the highest pollutant emitters in this study due to the intentional removal of aftertreatment systems. Under hot-running conditions, HEVs, as expected, could achieve carbon-reduction benefits of approximately 30 % (i.e., lower CO2 emissions and fuel consumption) compared to their conventional gasoline counterparts, while no measurable reduction in pollutant emissions was observed except in NOX (~70 % reduction). In contrast, the cold-start extra emissions (CSEEs) of CO2 reached 120–364 g/start for these HEVs, even exceeding the maximum values of conventional gasoline vehicles. However, the higher CO2 CSEEs of HEVs can be far offset by their hot-running emission reduction benefits. For tailpipe pollutants, the CSEEs of the HEVs were reduced by 21 %–68 % on average in comparison to those of conventional gasoline vehicles. Furthermore, strong correlations (R2 values of 0.69–0.89) between the road grades and relative emissions were observed. These results can provide necessary information regarding the improvement of future LDPV emission models and inventories.

Study on Emission Characteristics and Emission Reduction Effect for Construction Machinery under Actual Operating Conditions Using a Portable Emission Measurement System (Pems).

With the acceleration of urban construction, the pollutant emission of non-road mobile machinery such as construction machinery is becoming more and more prominent. In this paper, a portable emissions measurement system (PEMS) tested the emissions of eight different types of construction machinery under actual operating conditions and was used for idling, walking, and working under the different emission reduction techniques. The results showed that the pollutant emission of construction machinery is affected by the pollutant contribution of working conditions. According to different emission reduction techniques, the diesel oxidation catalyst (DOC) can reduce carbon monoxide (CO) by 41.6–94.8% and hydrocarbon (HC) by 92.7–95.1%, catalytic diesel particulate filter (CDPF) can reduce particulate matter (PM) by 87.1–99.5%, and selective catalytic reduction (SCR) using urea as a reducing agent can reduce nitrogen oxides (NOx) by 60.3% to 80.5%. Copper-based SCR is better than vanadium-based SCR in NOx reduction. In addition, the study found that when the enhanced 3DOC + CDPF emission reduction technique is used on forklifts, DOC has a “low-temperature saturation effect”, which will reduce the emission reduction effect of CO and THC. The use of Burner + DOC + CDPF emission reduction techniques and fuel injection heating process will increase CO’s emission factors by 3.2–3.5 and 4.4–6.7 times compared with the actual operating conditions.

Investigation of real operation gaseous emissions from a diesel locomotive

• The high BSFC at the idle operation decreases as the BMEP increases. • Highest BTE at the mid-BMEP, corresponding to 50% load condition. • Total amount of gaseous emissions increases as the BMEP increases. • Lowest brake specific gaseous emissions at the mid-BMEP. • Test mode including high emission-measured condition provides with low uncertainty. Many investigations on the fuel consumption and the emission characteristics of diesel engines for non-road mobile machinery (NRMM) have been carried out in the various conditions of steady-state and transient operation, and the knowledge obtained from these studies provides substantial information to analyze real operation emissions. Detailed information on the fuel efficiency and the emission under the real operation condition, however, is still needed to provide significant information to develop the advanced after-treatment system as well as to analyse the fuel efficiency and emissions from the NRMM operating real-world conditions. This study aims to investigate the fuel efficiency and the gaseous emissions from a diesel locomotive. The experiment was carried out with a Portable Emissions Measurement System (PEMS), and studies the fuel efficiency, the overall gaseous emissions, the association of gaseous emissions and brake mean effective pressure (BMEP), and the load conditions for the emission measurement.

China 6 moving average window method for real driving emission evaluation: Challenges, causes, and impacts

The light-duty moving average window (MAW) method, used for China 6 real driving emission (RDE) calculation, is quite complex with various boundaries. Previous research noticed that the MAW might underestimate the calculation results, while the reasons for this underestimation haven't been studied systematically. With 29 vehicles tested in 10 cities and different boundaries applied for calculation, this study quantitively analyzed the problem, causes, and impacts of the light-duty MAW method. The instantaneous utilization factor (IUF) is proposed for reason analysis. The current MAW method could weaken the supervision of real driving tests as more than 75% of the tests underestimated MAW results, with the largest underestimation being around 100%. The data exclusion could lead to biased MAW results. But without the exclusion, the MAW result couldn't always get an increase due to the IUF and window weighting factor variation. With the extended factors removed, the MAW result bias is significantly reduced. The MAW will lead to a lower IUF of the data at the start/end of the tests, and when the cold-start data is considered, this low utilization must be noticed. The effect from the data exclusion, extended factors, and the window characteristics are closely coupled and they should be taken into consideration simultaneously to consummate the calculation method. The current drift-check progress couldn't effectively monitor the portable emission measurement system (PEMS), especially during the tests. The MAW result might lead to unreasonable emission limits and the emission inventory. Relevant policy based on these results might be implausible.

Analysis of Emissions and Fuel Consumption in Freight Transport

Currently in Europe, road freight transport is characterized by the most dynamic advancement. Year after year, we may observe an increase in the amount of transported goods. The paper presents the emissions of gaseous exhaust components such as CO, THC, and NOx as well as fuel consumption in freight transport. The emission analysis was performed for the entire transport cycle covering the handling of the goods with forklifts and carriage with a heavy-duty truck. The investigations were performed under actual conditions of operation using a Portable Emission Measurement System (PEMS). The fuel mileage was determined using the carbon balance method. The test routes were designed so as to reproduce the transport-logistic system typical of small towns. The setting for the tests was a town located in central Poland near the A2 motorway constituting part of the trans-European logistic network with multiple locations of logistic centers. In order to present the real emissions during handling, two test variants were considered: an outdoor variant (on a nearby lot) and inside a warehouse. The test run of the heavy-duty truck involved transporting 24,000 kg of load on urban and extra-urban (local and intercity) roads. The exhaust emissions and fuel mileage were determined for each of the stages as well as for the entire research cycle.

THE IMPACT OF DIESEL BUS EMISSIONS ON AIR POLLUTION IN ULAANBAATAR AND ATTEMPT TO REDUCE IT

The advantages of diesel engines have led it to become the only solution for heavy-duty vehicles (HDV), including city buses. Exhaust gas from diesel engines (EG) is a common environmental pollutant and carcinogenic to human health. The paper presents the results of measuring the emissions of city buses running on high sulfur fuel with and without diesel particulate filter (DPF). The study was conducted in real traffic conditions along the regular route of the city of Ulaanbaatar. The measurements were carried out using the HORIBA PEMS (Portable Emissions Measurement System) and the gravimetric method. The measured data was used to determine the actual emission levels from city buses. The actual particulate matter (PM) emissions from city buses were determined during the warm and cold seasons on a daily basis. It is found that a bus with average daily mileage of 242 km emits average of 166.155 g of PM into the atmosphere per day. This fluctuates depending on the season - 141.3 g in summer and 175.8 g in winter. The actual PM emissions of a city bus is 0.6866 g/km. The NOx concentration in the exhaust gases is 1410.94 ppm on average. As a result of 6 months of measurements, a total of 346.651 kg of soot was collected from 24 buses. Innovation: Actual on-road emissions from Ulaanbaatar buses and a cassette-type DPF system with “active” outside the bus regeneration, that can reduce conventional diesel engine PM emissions by up to 90% regardless of the sulfur content of the fuels.

Investigation into the Impact of Weight on Diesel Trucks’ NOx Emissions: An Overweight Case Study

To build an understanding of the emission contribution, especially nitrogen oxides (NOx) emissions, of many overweight/oversized trucks operating in the Dallas-Fort Worth area, U.S., the North Central Texas Council of Governments commissioned the Texas A&M Transportation Institute to conduct an emission testing study. The study team collected and analyzed data on these vehicles’ activities and emissions characteristics. Vehicle activity data collection was performed using portable activity measurement systems, and exhaust emissions data was measured using two portable emission measurement systems. Using methodologies developed by the Environmental Protection Agency for the MOtor Vehicle Emissions Simulator (MOVES) model, both datasets were processed and expressed as emission rates for three loading scenarios. Researchers observed that, because of the sensitivity of the performance of selective catalytic reduction (SCR) to exhaust temperature, NOx data observed during a test cycle may not result in emission rates that are representative of the real-world operations. The team developed a methodology to adjust the resulting NOx rates for SCR-equipped trucks. The findings of the analysis suggest that the current MOVES opMode equations do not appear to adequately capture the impact of weight on the emission rates of heavy-duty diesel vehicles. The team also found that SCR-equipped trucks can have lower emission rates under heavier loads, especially in higher-speed and higher-power opMode bins, which typically have higher exhaust temperatures. Under normal loads (approximately 55,000 lb), SCR does not seem to provide a NOx emission reduction benefit at speeds under 50 mph compared with exhaust gas recirculation-equipped trucks.

Real-world emission factors for SUVs using on-board emission testing and geo-computation

A Portable Emissions Measurement System (PEMS) was used to measure emissions of five sports utility vehicles (SUVs) in a wide range of real-world driving conditions. The program included testing of fuel quality, coast-down and emissions in start, hot running and extended idling conditions. Geo-computation methods were used to add critical information (road gradient) to the PEMS data. Results from this study are generally in good agreement with international PEMS data. Hot running NOx emission factors are on average seven times higher than the type-approval limit for diesel SUVs, and they reach about 2100 and 400 mg/km in urban conditions for NOx and NO2, respectively. They are 7 (NOx) and 4 (NO2) times higher than current emission factors in COPERT Australia. COPERT Australia emission algorithms for CO2 are well behaved and the PEMS data suggest an update is not required. COPERT Australia emission algorithms should be revised for diesel SUVs (NOx, NO2) and petrol SUVs (CO, THC, NO2) to ensure accurate estimation of vehicle emissions at fleet level. Inclusion of logistic regression is proposed for future COPERT updates.

Quantifying the Impact of Alternative Bus Stop Platforms on Vehicle Emissions and Individual Pollution Exposure at Bus Stops.

Due to stop-and-go events, bus stops are often treated as “hot spots” for air pollution. The design of bus stops should be optimized to reduce emissions and exposure for transit commuters. The objective of this study was to analyze the impact of bus stop platform types on vehicle emissions and individual pollution exposure. Second-by-second emissions data were first collected from one bus using a portable emission measurement system (PEMS). Microscopic traffic simulation was then used to estimate overall traffic emissions under six scenarios with different bus stop settings. Numerical simulation of pollutant dispersion was also conducted to calculate individual pollution exposure at bus stops. The results of PEMS tests showed no significant differences between bus emissions generated near two different types of stops. However, the effect of platform types on overall traffic emissions was revealed using traffic simulation. The results demonstrated that bus bays reduced the emissions of other heavy-duty vehicles. However, bus bays were not always effective during rush hours. The study also highlighted the importance of the location of bus stops, the number of bus lines, and the length of the platform, in addition to dynamic characteristics of traffic flows in the design of bus stop platforms. Bus stop platforms also affected individuals’ exposure due to the changes in the pollutant flow field. The passenger’s exposure at one bus stop was influenced by both the platform type and standing location. Results suggested that in a condition with a wind direction perpendicular to the bus stop shelter, the total exposure level to CO was lower at the bus bay stop if a passenger stood at the upstream of the station platform. However, the exposure was less at the downstream of the curbside bus stop.

Assessment of On-Board and Laboratory Gas Measurement Systems for Future Heavy-Duty Emissions Regulations.

Road transport contributes significantly to air pollution in cities. Regulations across the globe continuously reduce the limits that vehicles need to respect during their lifetimes. Furthermore, more pollutants are being subject to control with new regulations and, most important, testing tends to be done under real-world conditions on the road. In this study, various portable systems were compared with laboratory-grade equipment with a wide range of emissions, focusing on the lower end, where the measurement uncertainty of the instruments is crucial for the determination of emission limits. The engines were diesel- and compressed natural gas (CNG)-fueled. The results were promising, with relatively small differences between portable emissions measurement systems (PEMSs), portable Fourier transform infrared (FTIR) and quantum cascade laser infrared (QCL-IR) spectrometers, and the respective laboratory-grade analyzers based on chemiluminescence detection (CLD), non-dispersive infrared (NDIR), and FTIR principles. The results also highlighted the need for strict technical regulations regarding accuracy and drift for low emission limits in future.

In-Use Passenger Vessel Emission Rates of Black Carbon and Nitrogen Oxides.

This study quantified emission factors of black carbon (BC) and nitrogen oxides (NOx) from 21 engines on in-use excursion vessels and ferries operating in California's San Francisco Bay, including EPA uncertified and Tier 1-4 engines and across engine operating modes. On average, ∼60 fuel-based emission factors per engine were measured using a novel combination of exhaust plume capture combined with GPS location and speed data that can be more readily deployed than common portable emissions measurement systems. BC and NOx emission factors (g kg-1) were lowest and least variable during fast cruising and highest during maneuvering and docked operation. Selective catalytic reduction (SCR) reduced NOx emissions by ∼80% when functional. However, elevated NOx emissions that exceeded corresponding exhaust standards were measured on most Tier 3 and Tier 4 engines sampled, which can be attributed to inactive SCR during frequent low engine load operation. In contrast, BC emissions exceeded the PM emission standard for only one engine, and SCR systems employed as a NOx reduction technology also reduced emitted BC. Using these measured emission factors to compare commuting options, we show that the CO2-equivalent emissions per passenger-kilometer are comparable when commuting by car and ferry, but BC and NOx emissions can be several to more than ten times larger when commuting by ferry.

Impact of ethanol-gasoline implementation on vehicle emission based on remote sensing test

The vehicle exhaust remote sensing system was used to quantify the carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NO) concentrations of vehicles before and after the ethanol-gasoline implementation. The purpose was to investigate gasoline vehicle emissions for two distinct periods: before and after the ethanol-gasoline implementation. A comprehensive vehicle emission remote sensing data set collected in 2018 and 2019. The remote sensing test data was screened for duplicate vehicles in both two years. The average emission concentration of HC-CO-NO showed a continuous downward trend after ethanol-gasoline implementation. The three pollutant emission factors of small passenger cars are all lower than those of light trucks. Overall, the HC-CO-NO emission factors obtained through remote sensing tests have a small range of variation. From the results of the two-year test data, the emission levels of the 10% worst emission vehicles have shown a certain reduction compared with before the ethanol-gasoline implementation. Compared with random test errors of dynamometer emission test and portable emission measurement system, statistical results based on remote sensing test big data are more accurate.

Intermodal comparison of tailpipe emission rates between transit buses and private vehicles for on-road passenger transport

Modal shift from private vehicles (PVs) to transit buses has the potential to reduce energy use and emissions from on-road passenger transport. Comparisons between these modes may be sensitive to key factors, such as vehicle size, fuel and powertrains, passenger load, and travel routes. The objectives are to evaluate the sensitivity of emission rates to route alignment, and compare emission rates between PVs and buses accounting for variability in key factors. Real-world bus speed trajectories were measured on actual bus routes for four origin-destination pairs (ODPs). To evaluate the sensitivity of emission rates to route alignment, hypothetical alternative bus routes were posited based on shortest distance, shortest travel time, or observed PV routes for each ODP. Trajectories and emission rates for PVs were quantified based on prior measurements of two routes per ODP using portable emission measurement systems. Trip-based tailpipe CO2, CO, total hydrocarbons (THC), NOx, and particulate matter (PM) emission rates were estimated for each ODP for gasoline and gasoline-hybrid PVs based on a Vehicle Specific Power modal model and for compressed natural gas, diesel, and diesel-hybrid buses based on the Transit Bus Emissions Model. Break-even passenger load (BEPL) was quantified to assess the minimum bus passenger load needed to achieve lower per passenger-trip emissions compared to PVs. Bus emission rates per bus-trip on actual bus routes are generally higher than those on hypothetical routes. As a bounding analysis, compared to single-occupancy PVs, fully occupied buses are estimated to have 82%–94% lower CO2, 99% lower to 308% higher CO, 99% lower to 145% higher THC, 67% lower to 62% higher NOx, and 94%–99% lower PM emission rates per passenger-trip depending on vehicle size, fuel and powertrain, passenger load, and route. BEPL varies depending on vehicle size, fuel and powertrain, route, and pollutant. The relative importance of key factors affecting intermodal comparisons differs by pollutants. The intermodal comparison is also affected by interactions among key factors, such as passenger load and route alignment, which reinforces the need for joint consideration of key factors.

Hybrid Vehicles as a Transition for Full E-Mobility Achievement in Positive Energy Districts: A Comparative Assessment of Real-Driving Emissions

Air pollution is a major concern, particularly in developing countries. Road transport and mobile sources are considered the root causes of air pollutants. With the implementation of zero-carbon and zero-energy concepts at the district scale, cities can make great strides towards sustainable development. Urban planning schemes are moving from mere building solutions to the larger positive energy district (PED) scale. Alongside other technology systems in PEDs, increased uptake of electro-mobility solutions can play an important role in CO2 mitigation at the district level. This paper aims to quantify the exhaust emissions of six conventional and two fully hybrid vehicles using a portable emission measurement system (PEMS) in real driving conditions. The fuel consumption and exhaust pollutants of the conventional and hybrid vehicles were compared in four different urban and highway driving routes during autumn 2019 in Iran. The results showed that hybrid vehicles presented lower fuel consumption and produced relatively lower exhaust emissions. The conventional group’s fuel consumption (CO2 emissions) was 11%, 41% higher than that of the hybrids. In addition, the hybrid vehicles showed much better fuel economy in urban routes, which is beneficial for PEDs. Micro-trip analysis showed that although conventional vehicles emitted more CO2 at lower speeds, the hybrids showed a lower amount of CO2. Moreover, in conventional vehicles, NOx emissions showed an increasing trend with vehicle speed, while no decisive trend was found for NOx emissions versus vehicle speed in hybrid vehicles.

Numerical study on the regeneration characteristics of catalytic diesel particulate filter based on real driving emissions in plateau environment

In order to study the regeneration characteristics by O2 and NO2 of CDPF (Catalytic diesel particulate filter) at different altitudes, the atmospheric environmental parameters and exhaust emissions under the real driving condition were measured on a pickup truck equipped with the AVL M.O.V.E. PEMS (Portable Emission Measurement System) at average altitudes of 0 km, 2 km, 4 km, respectively. Then a finite rate regeneration reaction model was established. The numerical results show that the regeneration balance cannot be achieved in plateau environment based on the original emission. Through the single factor method, the effects of the exhaust temperature, the mass ratio of the NOx to PM, the oxygen concentration and the ratio of the engine displacement to the filter volume on the soot oxidation rate were simulated. The results show that in order to achieve regeneration balance, the exhaust temperature should be higher than 510 °C or the mass ratio of the NOx to PM should be greater than 70 at an altitude of 2 km, while the mass ratio of the NOx to PM should be greater than 98 at an altitude of 4 km. However, regeneration balance cannot be achieved by changing other single factors. Furthermore, through the orthogonal experimental design, it is found that the exhaust temperature and mass ratio of the NOx to PM are the dominant factors affecting the O2-NO2 regeneration in plateau environment. The maps of the exhaust temperature coupled with the mass ratio of the NOx to PM on soot oxidation rate by O2-NO2 were drawn, which provide a theoretical basis for the regeneration and allocation of the diesel particulate filter in plateau environment.

Effect of diesel particulate filter regeneration on fuel consumption and emissions performance under real-driving conditions

Diesel particulate filters (DPF) are widely adopted in diesel vehicles to meet the increasingly stringent emission regulations, which require continuous passive regenerations or/and periodic active regenerations to burn off the accumulated particulate matter (PM). In spite of many laboratory studies using DPF benches and engine/chassis dynamometers, there is currently a lack of investigation on DPF regeneration under real-world conditions. Therefore, this study was conducted to investigate the impact of active DPF regenerations on the fuel consumption and gaseous and particulate emissions performance of a diesel light goods vehicle under real-driving conditions by using the state-of-the-art portable emission measurement system. In total, 60 real-driving emission (RDE) tests (∼1200 km in total) were performed on the same route during the same periods of a day, to minimise the effect of uncontrollable real-world factors on the performance evaluation. The results showed that real-world active DPF regenerations occurred every 130 km for the studied vehicle. Although they did not occur frequently, DPF regenerations increased the trip-averaged fuel consumption rate by 13% on average. CO and THC emission factors tended to increase with DPF regenerations because the post combustion used to achieve the high exhaust temperature for regeneration of the filter occurred under oxygen-lean conditions. Total NOx emissions were not affected but NO2/NOx ratio was greatly reduced by DPF regeneration due to lower NO oxidation by the diesel oxidation catalyst and higher NO2 reduction by the DPF. Finally, DPF regenerations sharply increased PM emission factors by 27 times compared with a trip without DPF regeneration, resulting in significant exceedance of the emission limit.

Effects of Polyoxymethylene Dimethyl Ethers Addition in Diesel on Real Driving Emission and Fuel Consumption Characteristics of a CHINA VI Heavy-Duty Vehicle

Polyoxymethylene dimethyl ethers (PODE), as the most potential oxygenated alternative fuel for diesel engines, is widely investigated. Considering the importance of research on real driving emissions (RDE) and the few studies focus on the emission characteristics of the PODE/diesel blended fuels under real driving conditions, a portable emission measurement system (PEMS) was applied to measure the RDE of a heavy-duty tractor fueled with diesel or PODE/diesel blends. The tests were carried out in accordance with the relevant regulations of the CHINA VI emission standards. The second-by-second data from PEMS and the OBD system were utilized to construct engine transient operating maps. The results indicated that the addition of PODE can still decrease CO and PN emissions significantly under real driving conditions, although the low load conditions are still the areas of high brake specific CO and brake specific PN emissions. The NOx emissions, however, were not reduced as the results of the steady-state experiment of the same model of the engine. Fuel mass consumption raised when PODE was added, while the overall brake thermal efficiency improved, especially for the blending ratio of 30%, up to 40.3%, which is higher than 38.4% of pure diesel operation.

Characterising the silver particle generator; a pathway towards standardising silver aerosol generation

Reference aerosols for the calibration of common aerosol instruments such as condensation particle counters (CPCs) and differential mobility analyzers (DMAs), must fulfill certain criteria. The aerosol must be stable and reproducible in particle size and number density, ideally be monodisperse and nonvolatile and comprise a uniform non-reactive material. To this end, a new Silver Particle Generator (SPG) from Catalytic Instruments (Catalytic Instruments, Rosenheim, Germany) was characterized extensively with regard to aerosol properties within an overall framework of operator convenience. The SPG produced number densities up to around 2 × 1010 cm−3 of thermally stable, solid, unimodal aerosol with geometric standard deviation smaller than 1.45. The aerosol production in the SPG resembles that of a classic tube furnace, however, the device is easier to set up and configure, and offers long-term stability using controlled standardized procedures and operation settings. The SPG has two operational modes (simply, Modes 1 & 2 for the smallest and largest aerosol, respectively). The aerosol exhibited an intraday stability and day-to-day reproducibility in geometric mean mobility diameter (GMDmob) within a standard deviation of 4%. Based on measurements by transmission electron microscopy (TEM), particles from Mode 1 were spherical when default settings (air as carrier/dilution gas) were applied, whereas larger particles from Mode 2 comprised both compact near-spherical particles, and larger aggregates. Switching to nitrogen as a carrier gas and sintering at 800 °C reshaped the aggregate fraction of the aerosol from Mode 2 into uniformly spherical particles. Suitable applications of the SPG include the calibration of CPCs, DMAs, particle measurement program (PMP)-compliant measurement including particle number counters (PNCs) and the characterization of complete particle number - portable emissions measurement systems (PN-PEMS) systems and other particle counters for air quality monitoring.